The present invention relates to a thin film transistor liquid crystal display (TFT-LCD) array substrate and a method of manufacturing the same.
A thin film transistor liquid crystal display (TFT-LCD) has the advantage of small volume, low energy consumption, low radiation, and etc., and thus prevails in the flat panel display market.
A TFT-LCD typically comprises an array substrate and a color filter substrate that face each other. The array substrate is provided with thin film transistors and pixel electrodes, arranged in matrix, each pixel electrode being controlled by a thin film transistor. The pixel electrode is charged when the thin film transistor is on. After charging, the voltage of the pixel electrode remains unchanged until recharging at the time of next scanning. Generally speaking, the capacitance of liquid crystal is small; and thus mere capacitance of the liquid crystal is not able to sustain the voltage of the pixel electrode. For this reason, it is worth providing a storage capacitor to sustain the voltage of the pixel electrode. In principal, a storage capacitor is categorized as a storage capacitor on a gate line (Cs on Gate), a storage capacitor on a common electrode line (Cs on Common), or a combination structure thereof. The combination structure refers to a structure where a portion of the storage capacitors is formed on a gate line and another portion is formed on a common electrode line.
Regardless of the types of the storage capacitor, the gate metal thin film is used as an electrode plate of the storage capacitor. A gate insulating layer and a passivation layer are interposed between the gate metal thin film as one electrode plate and the pixel electrode as another electrode plate of the storage capacitor. The gate insulating layer may have a thickness of 3000 Å-5000 Å, and the passivation layer may have a thickness of 1500 Å-3500 Å. From the formula to calculate the storage capacitance, the value of the storage capacitance in unit area is in inverse to the distance between the two electrode plates. Because the distance between the two electrode plates of the storage capacitor in a conventional TFT-LCD array substrate is great, the storage capacitance in unit area is relatively small.